The present invention relates to an apparatus for applying labels to objects, such as bottles or the like, comprising at least one moveable gluing palette which is intended to coact with a rotary gluing roller so as to be coated with glue and thereafter to transfer glue to a label which is transported by the palette from a label magazine to a gripper which is intended to grip the glue-coated label and press the label onto the object concerned.
Devices of the aforedescribed kind are used, among other things, to apply labels to bottles in breweries, soft-drink bottling plants and like plants, which require the labelling devices to operate at high speed. The majority of these devices include a rubber gluing roller, aluminium gluing palettes and an adjustable glue scraper which is operative in determining the thickness of the glue on the gluing roller.
These known devices must be produced with extreme accuracy and any subsequent adjustments to the devices in operation must be effected very precisely, since, for instance, the gluing palettes may only partially penetrate the glue layer on the gluing roller without making contact with the outer surface of the roller itself, since such contact would force the glue layer carried by the roller out onto the edges of the palette. This would cause glue to splash or squirt onto the palette surroundings, and would also result in glue fastening to the front side of the labels, causing the labels to be drawn off the bottles. Loose labels which fasten to the gluing roller are difficult to remove and may result in damage to the roller, particularly when using foil labels, since such labels can cause wear on the roller when fastening between the glue scraper and the roller. A certain amount of wear can also be caused when the operator scrapes away labels that have fastened to the gluing roller with the aid of a sharp tool.
Another serious drawback with the known apparatus is that labels which fasten between the glue scraper and the gluing roller are liable to prevent the application of a fresh layer of glue on the roller, meaning that subsequent labels will not be completely coated with glue and that these glue-depleted labels will not stick to the very fast moving bottles. This may make it necessary to remove from the production line a very large number of bottles which lack labels.
Another factor is that the clearance between the gluing palettes and the gluing roller must not be excessive, since an excessive clearance will prevent the palettes from coming into contact with the glue, with the result that the labels will not be adequately coated.
The known apparatus are thus very sensitive to non-roundness of the gluing roller and also to wear on said roller, and require precise and play-free journalling of the roller.
DE-A1-3 131 164 describes a gluing machine or apparatus in which the gluing palettes are permitted to make contact with the gluing roller, wherein both the palettes and the roller are provided with mutually intersecting grooves. This arrangement, however, suffers several drawbacks, since, among other things, the ridges located between the grooves become coated with intersecting glue beads which are pressed out onto the edges of the palettes as the ridges come into contact with one another and splash down onto the surroundings and also result in glue fastening to the front side of the label.